With a miniaturization of semiconductor device, various semiconductor films are more and more used in the semiconductor device, and the requirements for parameters of the semiconductor films are increasingly strict. The parameters mainly include a thickness, temperature and reflectivity of the semiconductor film.
During a growth of the semiconductor film, usually a surface temperatures of the film need to be measured. In an existing technology, the temperature of the film may usually be measured and calculated by following formula:E=(1−R)×Lb(λ,T)  (1)
Where in the formula (1), E is a thermal radiation value of the film, R is a reflectivity of the film for a light with a wavelength λ, Lb(λ, T) is a value of blackbody radiation of the light with the wavelength λ in the reaction chamber at a temperature T.
However, during the growth of a film, with the changing of film thickness, an interference effect of the film successively fluctuates, and thus the reflectivity R of the film for light is also successively changed. However, the changing of the reflectivity R is not considered in formula (1), which results in a difference between a measured temperature and an actual temperature of the film, and an inaccurate measurement result. Due to an oversimplification of formula (1), the result calculated from the formula (1) may be acceptable at a low temperature or a low measurement precision requirement, but at a high temperature and a high measurement precision requirement, this calculation method can not meet actual technological requirements. For example, in metal organic chemical vapor deposition (MOCVD), the temperature inside the reaction chamber is up to over 1000 Celsius degree and even up to 1200 Celsius degree. At the same time, a temperature difference in a space with a diameter larger than half meter is less than 1%, i.e., about 10 Celsius degree. In this condition, some factors influence the detecting accuracy of radiation value, for example, other minor factors in the reaction region, such as background radiation, loss in optical transmission etc., can results in a distortion of the detected temperature, which is unable to meet the requirements of industrial applications. Therefore, a high precise method for measuring a temperature at a high temperature (≧300 Celsius degree) is needed.